The investigations in this application propose to study the meiotic characteristics of the adult male and female Turkish hamster during prehibernation, hibernation and recrudescence in a short photoperiod/cold environment. Analysis of key steps in meiotic progression will be carried out simultaneous with relevant endocrine and thermal determinations. In the male, it is proposed to study the kinetics of meiotic stages, and analyze the duration of preleptotene DNA synthesis and replicon characteristics. Analysis of pachytene spermatocyte chromomere maps, synaptonemal complexes and Z-DNA sites is proposed. Recombination as assessed by chiasma will be done in diplotene spermatocytes with identification of individual bivalents by chromomere maps. Extraction and assay of recombination proteins will be made as one index of the normalcy of underlying genetic recombination. Chromosomal complements at metaphase I and II spermatocytes provide measures of fidelity of earlier stages and induced aberrations. The focus of investigation under defined photoperiod/temperature conditions in female Turkish hamster oogenesis will be to identify aneuploidy and structural abnormalities in oocytes matured in vitro and in vivo. It is also proposed to assess fertilized oocytes for transmissible abnormalities which may have been induced. The capability for studying the recrudescence of spermatogenesis and the later stages of oocyte maturation in a physiological condition using reduced temperature, a known perturbator of meiosis, as a probe presents a unique system for analyzing essential stages of germ cell development in mammals and correlating these with endocrine factors. The feasibility of the such studies has been demonstrated in a preliminary study with male Mesocricetus auratus.